Species : Oncomelania Hupensis Quadrasi

Draft risk assessment report addressing Terms of Reference Species : Oncomelania hupensis quadrasi 1. Taxonomy of the species Phylum Mollusca Class Gastropoda Family Pomatiopsidae Oncomelania hupensis quadrasi also known as Oncomelania quadrasi is a subspecies of Oncomelania hupensis – wild type strains only. Another subspecies (Oncomelania hupensis hupensis) is already on the Live Import List. 2. Status of species under CITES This species is prevalent in large numbers in several regions of the Philippines [1-4]. The species is not listed in CITES. The snails to be imported are derived from laboratory stocks maintained in the Philippines and/or the USA. The laboratory strain has been obtained from wild populations in the Philippines and has not been genetically modified. Occasionally, it may be necessary to source infected snails from wild populations to ensure the lab stocks do not become less pathogenic than endemic isolates. 3. Ecology of the species Oncomelania quadrasi is a tropical, freshwater snail that is operculated, amphibious and dioecious [1,2,4]. It feeds on green algae, diatoms and decaying vegetative matter. The snail lives in wet environments such as flood plain forests, swamps and sluggish streams, ones usually clogged with vegetation [1,2,4]. The species is susceptible to desiccation in the absence of moisture for prolonged periods [1,2,4]. Life Span: The snail can live for about 4-6 months in the wild, though it can live substantially longer in laboratory conditions. Those snails used to maintain the Schistosoma japonicum parasite life cycle in the laboratory will be crushed to harvest the parasite after 3 months post infection [1]. Size and Weight Range / Identification: The snails are small, dextral and generally dark brown in colour with the adult no bigger than 4-6mm in length with 4-6 whorls or spirals in the shell. Except for fine axial lines of growth the shell is rather thin and smooth (see illustration). Males are smaller than females [1,2]. Natural Geographic Range: Oncomelania quadrasi is known to occur over most of Mindanao Philippines except in oriental Misamis, in most of Samar, in northeastern Leyte, around Lake Naujan in Mindoro, in Sorsogon in Luzon, and on the island of Siargao northeast of Mindanao [1-4]. These areas have no distinct dry season. Within the endemic islands the distribution is related to topography, usually flat. Habitat: These are varied and include flood plain forests, swamps, ponds, water logged grasslands and small sluggish streams. They must be freshwater, definitely not brackish. Most often found at sea level elevation, they can occur at higher altitudes. The most noted characteristic of the snail inhabited areas is their flatness which promotes the retention of water. The snail is not migratory, remaining within its established habitat. It has been observed that adult Oncomelania hupensis quadrasi can withstand desiccation for about 3 months and there is evidence to suggest that the snail is able to hibernate as a survival mechanism during adverse weather/habitat conditions but, if these are prolonged, it eventually dies [1]. 1 Habitat Requirements: Includes vegetation which provides shade and shelter from sunlight. Defined level of water with sloping banks or water edge which provides breeding or egg laying sites and relative clarity of water. It is believed that well oxygenated water is essential, levels of 3.8 – 9.85ppm of dissolved oxygen. They do not like stagnant and foul water. They appear to prefer a relative neutral pH of soil and water. Oncomelania quadrasi is a tropical, fresh water snail so warmer, humid conditions are best. Humidity of around 70-80% and temperatures between 20-30 degrees celsius with optimum being 26 degrees celsius. Mortality increases significantly at much lower temperatures [1]. Social Groupings: The species does not form social groups but do tend to be found in colony clusters. Harm to Humans: The species in itself does not harm humans however, it is the intermediate host and therefore, if infected, a carrier of the parasite, Schistosoma japonicum, which causes the disease Schistosomiasis in humans [3]. Diet: Green algae, diatoms, decaying vegetative matter. 4. Reproductive Biology Oncomelania quadrasi is dioecious with separate male and female individuals. Reproduction therefore requires copulation between sexes. However, studies have shown that continuous presence of males is not necessary as females, once fertilised, can continue to lay fertile eggs for several months. Sexual maturity is reached at 10-16 weeks or approximately 3.5mm in size. Copulation occurs both day and night. Eggs are laid singly on solid objects in the water surface and at inter-phase between water and soil on sloping banks. A fertilised female can lay 2 eggs every 5 days. Hatching occurs 10-15 days after oviposition. There is no evidence to indicate that the snails are able to hybridise with other snail species [1,2,4]. 5. Feral Populations There is no record of feral populations of this species in Australia or in other parts of the world. Pest Status: This species is not considered a pest in its natural range. Much of the potential risk relates to the ability of the snail to carry disease causing parasites infective to humans. 6. Environmental Risk Assessment It is possible that Oncomelania quadrasi could adapt well to the conditions of the tropical north of eastern Australia if released and potential for the species to compete with other snails in the fresh water environment. It is also possible that prolonged periods of drought would have the potential to decimate any colonies. The snail’s role as a potential pest is primarily due to its ability to carry human disease causing parasites. This risk potential is considerably reduced through factors of better sanitation conditions in Australia and the lack of a present reservoir of infected mammals. However, this species will only be imported for scientific research purposes and will be maintained in Biosecurity approved quarantine premises under strict regulatory controls. The laboratory at QIMR Berghofer has maintained the Oncomelania quadrasi snails for 25 years. Last imported in 1999. Strict and diligent controls on the snails and the parasites have ensured that there has been no release of live snails or viable tissue from this laboratory. 7. Likelihood that the species could establish a breeding population in Australia. Oncomelania quadrasi could potentially establish a breeding colony if released from human control in a suitable fresh water habitat in a tropical region of adequate rainfall and humidity such as the tropical north east area of Queensland. However, there are several factors that may limit the snails ability to thrive and spread here in Australia. The snail is susceptible to desiccation in prolonged dry periods where the shallow 2 waters which it inhabits dry up [1]. The young snails, upon hatching, are primarily aquatic for the first two weeks becoming amphibious later [1,2,4]. It is at this stage that the snails are most vulnerable to dry conditions, though the adults have the ability to survive longer as they are able to aestivate in dry conditions. It does not thrive at colder temperatures, the optimum being around 26 degrees celsius and mortality increases significantly when temperatures drop below 10 degrees [1]. It does not tolerate stagnant, foul water, requiring well oxygenated water of relative clarity. The snails are not compatible with fast currents, requiring slow, sluggish water movement [1]. Unlike a number of snail species which are hermaphrodite and thus capable of self fertilisation, the Oncomelania quadrasi is dioecious with separate male and female individuals requiring copulation between sexes to breed. This can be a major limiting factor. 8. Potential impact of the species should it become established in Australia The species feeds on green algae, diatoms and decaying vegetative matter in freshwater locations. In such a habitat it could compete with other small aquatic snails. The species is unlikely to affect agriculture or contribute to land degradation. The risk to humans from this species lie in its capacity as an intermediate host to the pathogenic blood fluke Schistosoma japonicum which causes the disease Schistosomiasis. These parasites infect humans by penetration of the skin in freshwater environments. Though very host specific with regard to the snail host it is not limited to humans as the primary mammalian host, being infective to several mammalian species including cows, pigs, dogs, goats, rats and mice, rabbits and hares. It is possible that it may also be infective to several native species. Maintenance of the life cycle of Schistosoma japonicum in natural environments in Australia is highly unlikely as it would require 1. An established colony of Oncomelania quadrasi 2. Infected human or animal to defecate into the body of water where the snail host occurs. 3. Frequent visits of potential mammalian hosts to that water body. While it is likely that humans in Australia carry the disease, the prevalence is quite low (limited to travellers or immigrants from the endemic areas of the Philippines) and too low to sustain a viable risk. It is extremely unlikely that there are any infected animals present in Australia outside the strict controls of Biosecurity containment facilities at research institutes. 9. Restrictions This species should only be imported for the purposes of research where strict Biosecurity controls are enforced. The parasites will be sourced from laboratory maintained stocks that have not been genetically modified. It may be necessary on occasion to refresh these stocks with wild sourced infected snails to ensure that the life cycles that the research is being conducted on do not become less pathogenic than that occurring in the natural environment. The snails should be transported by approved couriers or accredited Biosecurity approved persons in approved biological containers which meet IATA standards.

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